This competitive revision application seeks additional funding for new aims that are being proposed for original grant application RO1EY10343. The original application sought funds to further our studies of the mechanisms of ischemic preconditioning (IPC) in the rat retina in vivo. IPC is a brief period of ischemia that is capable of inducing robust tolerance to the effects of damaging ischemia. Thus, IPC provides neuroprotection, and the study of its mechanisms is expected to lead to clinically translatable means to prevent ischemic injury. Significant visual loss may result from retinal ischemia in retinal arterial or venous occlusion, glaucoma, atherosclerosis, or in systemic disorders such as diabetes mellitus. Because treatment of these disorders remains unsatisfactory, the prospect of activating endogenous neuroprotective mechanisms is exciting and of significance to preventing these disorders that result in significant disability. We also recently observed that an even more robust neuroprotection could be induced by placing the brief ischemic stimulus AFTER the damaging ischemia, which is the reverse of the protocol used in preconditioning. This effect is known as post- conditioning. Preliminary data presented in this proposal support the protective effect of post-conditioning (Post-C), but also suggest that the mechanisms, while related, may not be the same as IPC. Examining mechanisms of Post-C has the potential to yield new insights into endogenous neuroprotection in the retina. Moreover, Post-C, unlike IPC, may itself be directly applied clinically, after an episode of ischemia. Accordingly, we propose a competitive revision that will expand our studies into a new specific aim, i.e., to examine the mechanisms of Post-C. We hypothesize that Post-C alters the molecular environment of retinal cells during reperfusion following ischemia, via activation of MAP kinases. The research design in this competitive revision builds upon that used in the currently funded grant, adding detailed study of the MAP kinases. We will use innovative methodology developed during the current period, i.e., the use of interfering RNA to procude a targeted, specific knock down in vivo of MAP kinase subtypes. Combining state of art retinal functional electrophysiological assessment, histological examination, and characterization of cell death and molecular mechanisms by both well established and newer technologies, we will use a powerful and robust model to elucidate the mechanisms of a promising means to induce endogenous neuroprotection in the retina. PUBLIC HEALTH RELEVANCE: Combining state of art retinal functional electrophysiological assessment, histological examination, and characterization of cell death and molecular mechanisms by both well established and newer technologies, we will use a powerful and robust model to elucidate the mechanisms of a promising means to induce endogenous neuroprotection in the retina.